Idea: Adding a Numeric Quanitfier Feature for Grammars

[im-deepfriedwater]

It would be useful in certain situations to specify a numeric amount of repetitions. For example, in JavaScript regexes I could do:

/[0-9A-F]{4}/i

Ohm could have similar convenience benefits, especially if a user might want a rule to require a specified amount of "things" without having to copy and paste said "thing" for however many repetitions they want.

[MuhammedZakir]

From #310 :

@MuhammedZakir Can you add some more details about your use case to #215?

Before going further, I would like to mention that I didn't "need" numeric quanitifer as much as I thought I would.

I was trying to write a grammar for Markdown parser according to CommonMark spec [1]. As you know, in Markdown, indenteding a line by 4+ spaces [2] will make it a code block. For this use case, I use lookahead for a string of 4 spaces. This works for me and I personally didn't need this feature (at least for now).

However, I can see this will be slightly ugly if, for example, trying to match a rule or a bigger string x number of times. This will also be problematic if there are a bunch of rules where we need an exact number of matches. Dong the way I am doing right now will make the grammar too verbose (which make it harder to read) and error-prone (when modifying).

Re: about using semantic action: I gave it some thought, but didn't like it (for my case). Because if I do it like that, I will have to parse each block again if the indentation is less than 4 spaces. This is probably not a problem per se, but I find this unsatifactory.

[1] https://spec.commonmark.org/0.30/
[2] 4 spaces or 1 tab or a mixture of them